Var.calc in Match()

Does anyone else find that using the Var.calc option (for
heteroscedasticity consistent std. errors) in Match() (from the
Matching library) slows down computation of the matching estimator by
a lot?

I don't really understand why when I use this option it slows down so
much, but for me it does significantly. I want to use the
heteroscedasticity consistent std. errors in my project, but as long
as it takes to compute them, I don't know if I will be able to.

Thanks,

BQ